The receiver location Engel want us to use is indeed very limited in space.
Your suggestion sound ok but I really do not know if the electrical motors will cause problems, they are indeed suppressed but I dont know how it will work.

Your sub looks great - your workmanship is very neat and precise. I am starting to convert the new Revell Type IX to RC and the watertight compartment will be very narrow. I like your method to seal the dive planes push rods and would like to know where you get the rubber bellows that seal the ends. As I am not sure of the correct technical name I am not sure where to look. Any help would be gratefully appreciated.

Sorry about the very lengthy delay in responding but the sub has been on the back burner awaiting the completion of another project as mentioned above.

About the only RX that I find suits is the Sombra Labs 8Ch RX no longer available. I am fortunate to have a pair. The RX is at the very forward end of the WTC as suggested by Engel. What I would like to know is what is the source for 75MHZ Receivers that will fit in that area. I am thinking that there must be some 40MHZ RX's that fit the bill.

I forgot to ask if you are designing your own WTC or using one of the Merriman WTCs. He specializes in WTC for the 1/72 submarines. If using one of his, all the necessary parts are supplied. He uses seals to keep the WTC integrity and Engel uses the bellows for WTC integrity.

I've been away from this project for a while but it is time to get the WTC installed into the hull. I started working on the lead for the ballast but it occurs to me that the Sub-C battery pack is much lighter than the D-Cell pack. A question for Jan if you are still following. How much lead ballast did you use in your Engel Type VII/C. He supplies about 1KG of lead in 4 strips and if you follow the plan, you use up all but 600mm of one of the lead strips. However, this is for the Battery Pack with 20 D-Cells. My pack has 24 Sub-C Cells and would you believe, about 1600 grams lighter. I assume I have to add 1600 grams of lead to make up the difference. I have an email to Engel but perhaps you have worked out the ballast for your build.

There are RX's like the one mentioned above, the problem being that that it will be very difficult to get the connectors on if at all possible. In Europe there are a number of 40MHZ RX's that will work. In fact, Engel has one on the website now. The connectors need to come straight out of the end of the RX. The only candidate at 75MHZ is the Sombra Labs (No longer available). It the FCC would allow 40MHZ here in the US most of the problems would be solved but that is not likely.

The lead ballast showed up today so it's on with getting it into the hull. Unfortunately I did not get feedback on the weights of the battery packs so I had to do a little averaging. The 8000Mah D cells range from 135 to 145 grams. I used the average of 140 grams to get 2800 grams for the old 20 cell pack. The Sub-C cells range from 55 to 65 grams. I used an average of 60 grams to get 1440 grams for the the new 24 cell pack. The difference being 1360 grams or about 48 ounces. The final trimming of the boat, both to the water line and fore/aft will have to take place once the boat is finished and in the water.

The picture shows three bags of lead shot at 1 pound per bag. I need to add the rest of the bar lead per the print and then spread the shot evenly between. An addition of resin to keep the shot in place will probably add and ounce or so, well within the margin of error on the battery weights. Who knows.

Next update, ballast installed.

Until next time,

IR3

Images

I mixed up some finishing resin and made a soup of 3lbs of shot and resin. It was poured into the center area between the lead strips and smoothed out. A check was made to ensure that there would be no interference with the WTC tube. The pics show the shot in place and the tiered assembly of the lead strips per the plans. One of the pics is slightly out of focus but the idea shows. The rings are the clamps for the WTC tube.

Next step is to get the foam cut and placed into the fuel tank blisters. Apparently there is a balance between the ballast and the foam and I have not found an explanation of this that I fully understand. I just hope that Engel is correct on the amount of foam and ballast.

Next update will be installation of the foam.

Until next time,

IR3

Images

The flotation foam has been carved and test fit. The WTC tube does not interfere so I will be filling the pores with resin and install them. The instructions call for installing them with no air pockets or places where water might collect. Good luck. There is no way I can check for this. I can't even see the fit for the floats in the aft section of the hull blisters. All I can say is that the WTC tube clears them. The kit manufacturer should have made these pieces. They have the molds that created the hull, thus they have all that is needed to make the floats and have a good fit. Having said that, I will be installing them with Gorilla Glue. Gorilla glue expands while curing and by applying aggressively, most of the space and maybe all will be sealed.

Thanks for the comment. Hopefully this is the last of the headaches building this sub. The WTC and the Tech Rack have been installed before so hopefully that will be the same and I can test for leaks, hopefully none. It's getting close.

hahahah...
Sorry, did you say you hope this is the last of the headaches?

Question comes to mind. Is you submarine in the water working perfectly?
If it isn't then, no the headaches are not over. In fact even if your boat is in the water, running, diving and surfacing, I can say that there are still headaches before you.

You can run a boat and it can be prefect. Then a month later you go to run the boat and something will need maintenance done.

But there is a bright side. If you take all of this as part of running a submarine then you will be okay.

Even the real boats come out of an overhaul and have issues to fix. "Sea Trials" to shake out all the bugs.

The floats have been sealed and installed. The floats at the aft end of the boat are the same size, just that the angle of the picture distorts the image. The WTC tube is in place but not permanently as of yet. The forward end that goes over the internal nose cone needs to be cleaned and silicon grease applier to help the O-ring seal. The picture with the slip rings does not show the O-ring in a groove around the outside. The WTC Tube slides over this cone and the O-ring supplies the seal. I included a picture of the internal nose cone installation to point out a problem. It will not affect the integrity of the nose cone itself.

The nose cone contains the forward dive plane servo and signals to that are passed by slip ring contactors on the tech rack (I can't seem to find that picture). The bottom bolt is impossible to put on as the end of the screw almost touches the fiberglass hull and I just can't get the nut on. The upper bolt, however, should suffice.

Now it is onto the completion of the Tech Rack wiring and preliminary checkout of all the functions.